The present invention relates to a method and apparatus for finding the range of a target object, and more particularly to a method and apparatus for finding the range to various points on the surface of the target object without relying upon assumptions about the shape of the object. The invention is particularly useful for ranging an object which is to be grasped by an industrial robot.
Many schemes for stereoscopically determining the range of a target object have been devised. In a typical "range finder" camera, for example, a view of the object is taken at a first position along a base line, this view is matched with another view taken at a second position along the base line, and triangulation is employed to determine the range in order to automatically set the lens. It is the photographer, of course, who matches the views, and this requires an exercise of judgment. In methods which determine range electronically, however, a problem which frequently arises is that of matching the view from one position with the view from another position. Typically this problem is solved by making assumptions about the target object. It may be treated as a point, for example, or it may be assumed to have an edge which is readily identifiable in electrical signals for both views. Such assumptions clearly limit the utility of the range finding method.